Pneumatic dust collection system

ABSTRACT

A pneumatic dust collection system includes a housing which defines a dust-air chamber portion, a flushing air chamber portion and a clean air portion arranged one above the other. A separating wall between the flushing air chamber and the dust-air chamber is penetrated by fittings for suspending filter hoses in the dust-air chamber portions which communicate through the fittings into the flushing air chamber. A connecting tube extends from the clean air chamber into the interior of each filter hose fitting and the filter hose which is carried thereby and defines an annular flow space between the interior of the hose and the flushing air chamber. This annular flow space may be closed off by an inflatable member which is disposed at the connection of the fitting to the separating wall. At this annular space the connecting tube includes a widened portion around which the flow is diverted and which is located opposite to the inflatable membrane. The interior of the inflatable membrane is connected to an air pressure line and it is inflated to close the annular flow passage between the interior of the filter hoses and the flushing air chamber. The apparatus includes a control system for controlling flushing air to the flushing air chamber and for filling this chamber before the membrane is deflated. An over and underpressure control is connected between the clean air chamber and the dust-air chamber to maintain a selected pressure difference between the clean air chamber portion and the dust-air chamber portion during operation. The flushing air chamber and the control line for supplying the air to the chamber is closed by a rapid depressurizer member which is closed by a signal from a preferred output of a monostable fluid mechanism element. An overpressure in he flushing air chamber causes the depressurizer to open rapidly.

United States Patent 91 Espeelet a1. 0

45] May 1, 1973 [5 PNEUMATIC DUST COLLECTION SYSTEM [76] Inventors: Frans Joris Espeel, Rosenbergstrasse 25, Oberuzwil; Ernst Ackermann, Egghalden, 9231, Egg/Flawil,

both of Switzerland [22] Filed: Aug. 24, 1971 [21] Appl. No.: 174,473

[30] Foreign Application Priority Data Primary Examiner-Dennis E. Talbert, Jr. Attorney-John J. McGlew et a1.

57 ABSTRACT A pneumatic dust collection s siemiiiifid'fib'ii ing which defines a dust-air chamber portion, aflushing ai'fhiihbeib'ifibizind a clean air po rtion arranged one above the other. A separating wall between the flushing air chamber and the dust-air chamber is penetrated by fittings for suspending filter hoses in the dust-air chamber portions which through the fittings into the flushing air chamber. A connecting tube extends from the clean air chamber into the interior of each filter hose fitting and the filter hose which is carried thereby and defines an annular flow space between the interior of the hose and the flushing air chamber. This annular flow space may be closed off by an inflatable member which is disposed at the connection of the fitting to the separating wall. At this annular space the connecting tube includes a widened portion around which the flow is diverted and which is located opposite to the inflatable membrane. The interior of the inflatable membrane is connected to an air pressure line and it is inflated to close the annular flow passage between the interior of the filter hoses and the flushing air chamber. The apparatus includes a control system for controlling flushing air to the flushing air chamber and for filling this chamber before the membrane is deflated. An over and underpressure control is connected between the clean air chamber and the dust-air chamber to maintain a selected pressure difference between the clean air chamber portion and the dust-air chamber portion during operation. The flushing air chamber and the control line for supplying the air to the chamber is closed by a rapid depressurizer member which is closed by a signal from a preferred output of a monostable fluid mechanism "elementfA n overpressure in he flushing air chamber causes the depressurizer to open rapidly.

17 Claims, 7 Drawing Figures communicate Patented May 1 1973 I 7 Sheets-Sheet l INVENTORS FRANS JOB/3 ESPEEL E RNS T 14C IfERMAN/V BY A rro/MEY Patented May 1, 1973 7 3,729,903

7 Sheets-Sheet 2 I IN V EN TOR-Y FRAMS' J'ORIS ESPEEL ER/VS T ACKER MANN A rmRNEF.

Patented May 1, 1973 3,729,1'9o3" 7 Sheets-Sheet 4 IN V EN TORS' WINS JDQ/S ESPEEL v ERNST ACKEKMA A/ V Patented May 1 1973 7 Sheets-Sheet 5 INVENTORS 'FQANS Ja /S 51955 zmysr ACAEQMAMV BY 'Patented May 1, 973 3,729,903

7 Sheets-Sheet 6 IN VEN TORS F2445 J02/S 5W6! 62/1/5 ACKR IANIV Patented May 1, 1973 7 Sheets-Sheet v INVENTORJ FRAMS Jae/5 55/ 564 1 PNEUMATIC DUST COLLECTION SYSTEM BACKGROUND OF THE INVENTION This invention relates in general to the construction of a pneumatic dust collection system and in particular to a new and useful pneumatic dust collection system which includes a dust-air chamber portion, a flushing air chamber portion and a clean air chamber portion disposed in order so as to adjoin each other axially and being separated from each other by separating walls between each portion and which includes at least one filter hose disposed in a dust-air chamber with a connecting tube protruding axially into one end of the filter hose which connects the tube to the interior of the filter hose and with the clean air chamber, and which leaves a free annular space in a radial direction between it and.

the filter hose for the passage of flushing air from the flushing air chamber into the dust-air chamber, this passage being closable by an inflatable control member.

DESCRIPTION OF THE PRIOR ART Dust collection systems are known in which there is an annular canal around a connecting pipe which interconnects a dust-air chamber with a clean air chamber and which is closed off against the flushing air chamber by a sleeve of laminations surrounding the connecting tube, in order to generate during a flushing air blast a vibratory motion acting upon the filter hose. But this necessitates that the flushing air chamber can only be filled with flushing air upon the release of a flushing air blast so that an overpressure can be built up in the filter hose by the flushing aironly gradually, which greatly reduces the cleaning effect.

SUMMARY OF THE INVENTION The invention at hand aims at the improvement of an arrangement of the kind mentioned, to the end of generating in the filter hose a sudden overpressure by the rapid back flow of flushing air.

This aim is realized, according to the invention, in that an annular flow passage around the connecting tube is closable by an inflatable, rubber-elastic, annular membrane which is coaxial to the connecting tubes longitudinal axis and closes the annular canal when it is inflated by controlled air pressure while it opens the passage when it is in a depressurized condition. The interior of the annular membrane is connected to a com pressed air source through a system of tubular lines which is regulated by control members to pressurize or depressure the annular membrane selectively, as well as to fill the flushing air chamber with flushing air before depressurizing the annular membrane.

Accordingly, it is an object of the invention to pro vide an improved dust collection system which includes a housing defining a dust-air chamber portion, a flushing air chamber portion, and a clean air chamber portion arranged one after the other and separated by separating walls and which includes at least one filter hose in the dust-air chamber which communicates at its interior through a connecting pipe to the clean air chamber and which includes a closable annular space around the connecting pipe which provides a communication between the interior of the hose and the flushing air chamber which is openable and closable by an inflatable membrane.

A further object of the invention is to provide a pneumatic dust collection system which includes a control line connected to the flushing air chamber having a rapid depressurizing connection thereto for depressurizing the line in the event of an overpressure.

A further object of the invention is to provide an im proved depressurizing valve mechanism for a pneumatic dust collection system.

A further object of the invention is to provide a pneumatic dust collection system and associated control mechanism therefor which are simple in design, rugged in construction and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a betterunderstanding of the invention, its operating advantages and specific objects attained by its uses, reference should be had to the accompanying drawing and descriptive matter in which there is illustrated preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 5 is a diaphragm of the control mechanism for the pneumatic dust collecting system;

FIG. 6 is a vertical sectional view of a pressure switch associated with the air flushing chamber of the device; and

FIG. 7 is a view similar to FIG. 4 of another embodiment of the invention.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings in particular, the invention embodied therein in FIGS. 1 through 6 comprises a pneumatic dust collection system which, as shown in FIG. 1, includes a dust-air chamber portion 1 in which is disposed a multiplicity of vertically arranged filter hoses 2. Toward the bottom the dust-air chamber 1 is provided with a conical dust collection chamber 3 which is closable by means of a gate valve 4. Ending tangentially in the dust-air chamber a dust-air line 5 connects tangentially into the dust-air chamber portion. The dust-air chamber 1 is separated by a separating wall 6 from a flushing air chamber 7 which, in turn, is separated by a separating wall 8 from a clean air chamber 9 with a discharge nipple 10 for the clean air. On the outside wall of the flushing air chamber 7 are disposed several rapid depressurizers 11, one of which is visible in FIG. 1.

Each filter hose is fastened by means of a pipe clamp 12 to a piece of pipe 13 which serves as a suspension for the hose and is attached to the separating wall 6 by means of screws 14. A connecting tube 15, equispaced radially and laterally from the piece of pipe 13, leads axially from the clean air chamber 9 to the interior of each piece of pipe 13. The connecting tube forms part of a pneumatic valve generally designated 16. The actuation of the pneumatic valve 16 is effected by the rapid depressurizer 11 via a control line 17, which are connected to several valves 16 for simultaneous actuation. Through a supply line 18, the control line 17 is connected to a compressed air source 19 (FIG. 5) which, through another supply line 20 (FIGS. 2 and 5), conveys compressed air into the flushing air chamber 7. A branch line 21 each leads from the control line 17 to a valve 16. The control line 17 is connected into the rapid depressurizer 11 through an opening 22 in a side wall 100 of the housing.

The rapid depressurizer 11 has a cylindrical jacket 23 (FIGS. 2 and 3 in which is disposed axially and welded to the wall of the flushing air chamber 7 a cylindrical part 24. The free annular edge 25 of the cylindrical part 24 forms a valve seat for a rubber-elastic membrane 26. The jacket 23, equipped with venting openings 27, forms with the cylindrical part 24 a depressurizing chamber 29, the cylindrical part 24 forms with the membrane 26 a pressure chamber 28. By means of screws 30, screwed into matching tapped holes in the wall of the flushing air chamber 7, a ring 31 and a dome-shaped cover 32 are screwed to the jacket 23. The cover 32 is provided with a peripheral, annular groove 33, in which is inserted an annular bead 34 of the membrane 26. The head 34 is retained between the annular groove 33 and the ring 31. The membrane 26 has a central hole 35 which connects the pressure chamber 28 with a pressure equalization chamber 36. On the side of the pressure chamber 28 the membrane 26 is provided with a flat sealing surface 37, and on the side of the pressure equalization chamber 36 with a flat sealing surface 38. The cover 32 has a hole 39 and an external sealing surface 40. Attached to the cover 32, axial to the hole 39, by means of screws 41, are a first intermediate housing 42, a second intermediate housing 43 and a cover plate 44. Clamped between the intermediate housing 42 and the sealing surface 40 is a gasket 45, whereas a rubber-elastic membrane 46 and 47, respectively, is disposed between the intermediate housings 42 and 43 and between the intermediate housing 43 and the cover plate 44. The intermediate housing 42 forms a venting chamber 48 which communicates through a hole 49 with the outside atmosphere, and it further has a hole 49 coaxial to hole 39. The membrane 46 is provided with an axial hole 50. Axial to hole 50, the second intermediate housing 43 present an opening 51 which empties into a venting chamber 52 communicating through a hole 53 with the outside atmosphere. The cover plate 44 is provided with a connecting hole 54 which is axial to membrane 47 and which is connected through a line 65 to the output Yl of a correlated monostable fluid mechanism element M.

The rapid depressurizer described operates as follows: For the air pressure built up in the control line 17 by the compressed air source 19 to exist, the membrane 26 must make close contact with the valve seat 25 and must close the pressure chamber 28. For the membrane 26 to remain in the closed position shown in FIG. 3, the

compressed air must be able to flow from the pressure chamber 28 through the hole 35 into the pressure equalization chamber 36. If identical pressure conditions prevail in the chambers 28 and 36, the membrane 26 is being pressed against the valve seat 25 because the membrane 26 offers the pressure equalization chamber 36 a considerably greater area than it does the pressure chamber 28. For the pressure in the pressure equalization chamber 36 not to drop, the membrane 47 must be pressed against the opening 51 by a pulse from the monostable fluid mechanism element M (FIG. 2), thereby closing the opening 51 pressure-tight. This makes it possible for the air to get from the pressure equalization chamber 36 through the hole 50 behind the membrane 46. The air caught between the membrane 46 and the membrane 47 presses the membrane 46 against the opening 49, closing it.

To vent the control line 17, the permanent signal of the fluid mechanism element M to the membrane 47 is interrupted so that the latter will free the opening 51 (see FIG. 3). This causes the pressure of the air caught behind the membrane 46 to drop because it escapes to the outside through the opening 51 and the hole 53. The consequence of this pressure drop is that the overpressure prevailing in the pressure chamber 36 lifts the membrane 46 from the opening 49 so that the air caught in the pressure equalization chamber 36 can escape to the outside through the opening 49, the venting chamber 48 and the hole 49. When the pressure in the pressure equalization chamber 36 drops, the membrane 26 is placed in front of the hole 39 by the overpressure prevailing in the pressure chamber 28, and the compressed air flows out of the pressure chamber 28 into the venting chamber 29 and thence to the outside through the venting hole 27.

As soon as the permanent signal acts upon the membrane 47 via the connecting hole 54, it closes the opening 51. The air flowing from the pressure chamber 28 through the holes 35 and 50 is suddenly stopped and repulsed, thereby pressing the membrane 46 against the opening 49, closing it. The process is repeated with the membrane 26 which is pressed against the valve seat 25, thus again closing the pressure chamber 28.

The connecting tube 15 (FIGS. 2 and 4) is conducted through a circular opening 56 in the separating wall 6, said opening 56 being of larger diameter than the outside diameter of the connecting tube 15 so that the flushing air enters the filter hose 2 through a canal of annular cross section. The connecting tube 15 is provided with an annular bead 58 which serves as valve seat. Between a flange 59 and the separating wall 6 there is disposed a rubber-elastic annular membrane 60 which is put loosely around a ring 61. The ring 61 presents a concave surface 62 which faces the annular bead 58 and is equispaced from it and against which the annular membrane 60 rests during a flushing air blast. The pipe nipple 13, the annular membrane 60 and the ring 61 are fastened to the separating wall 6 by means of the screws 14. The ring 61 is provided with a pressurizing canal or passage 64, one end of which connects to the branch line 21, the other end ending in the concave surface 62.

When the membrane 26 shuts the pressure chamber 28 due to a control pulse from a fluid mechanism ele ment to the membrane 47 (FIG. 3), an overpressure builds up in the control line 17 (FIG. 2) which propagates through the branch line 21 (FIG. 4) and the pressurizing canal 64 between the annular membrane 60 and the ring 61 so that the annular membrane-in accordance with the position shown in dotted lines in FIG. 4is pressed against the annular head 58, closing the canal 57. If the pulse emitted by the fluid mechanism element to the membrane 47 (FIG. 3) is interrupted, the pressure in the branch line 21 drops and a flushing air blast occurs.

The lower part of the connecting tube may have various limital lengths L,, L, or L,,, as required. If, in accordance with length L,, the connecting tube 15 is shorter than the pipe nipple 13, the blast of flushing air pulls the air flowing into, the clean air chamber 9 back into the filter hose 2. i

If, in accordance with length I..,, the lower part of the connecting tube 15 is approximately of the same length as the pipe nipple 13, the blast of flushing air interrupts the clean air flow to the clean air chamber 9 without pulling the clean air back into the filter hose 2.

If, in accordance with length L,,, the connecting tube 15 is longer than the pipe nipple 13 in downward direction, the clean air can flow, at least in part, into the clean air chamber 9 during the flushing air blast.

As may be seen from FIG. 5, the dust collection system presents several rapid depressurizers 11 to 11", with each of which are associated severalvalves 16 (FIG. 2). A pressure P1 prevails in, the clean air chamber 9; a pressure P2 prevails in the flushing air chamber 7; and a pressure P3 prevails in the dust-air chamber 1. Disposed at the outside of the dustcollection system is an overpressure and underpressure differential switch 66 which is connected to the clean air chamber 9 through a line 67 and to the dust air chamber 1 through a line 68. The pressure differential switch 66 is settable to a certain pressure difference P3 Pl, at which it responds. If the pressure difference P3 P1 exceeds the value to which the pressure differential switch 66 is set, the latter gives a signal via a line 69 to the'control input ofa bistable element B with preferred initial position at the. output Y, (arrow), thereby initiating one or more flushing cycles, and keeping them up until the set pressure differential P3 P1 falls below the preset value of switch 66. The signal arriving at the control X, of thebistableelement B generates a signal at the output Y,, by means of which the bistable element B controls an amplifier 70 connected to the compressed air source 19. The amplifier 70 thereupon conducts, through a reducing valve 71, a supply current to the monostable elements M to M". At the same time, the amplifier 70 gives a signal to a pneumatic valve 72 which is opened for the duration of the signal. Due to the pneumatic valve 72 being opened, compressed air flows from the compressed air source 19 through a throttle valve 73 into the flushing air chamber 7. In addition, compressed air is introduced to the supply lines 18' to 18" through a throttle valve 74. All bistable elements B, B to B" communicate through a line 88 directly with the compressed air source 19 by which they are fed.

The flushing air chamber 7 is connected to a pressure switch 75. If the pressure P2 in the flushing air chamber exceeds a certain value, the pressure switch75 controls an Or-Nor key element 0, emitting a signal to its input X. An Or-Nor key element is an element having two outputs Y, and Y,, one of which, (Y,, is preferred) is a control for air flow flowing through its control input X as long as there is a signal through the preferred output Y2. When the control input X is closed, which means when the discharging control air flow is shut off, pressure is applied to the other. When. the control input x is reopened, pressure is again applied to the preferred output Y,. The Or-Nor key element 0 gives a signal from the output Y, to the inputs E, and E, of a pulse transmitter 76 designed as a binary counter. The pulse transmitter 76 has two outputs A, .and A,, one of which, A,, has the assignment of controlling the odd rapid depressurizers 11', 11" etc. and the other, A,, the even rapid depressurizers 11 1 1 etc.

Thus, as described with reference to FIG. 2, a flushing air blast can be sent into the filter hoses 2 correlated with a rapid depressurizer 11, the membrane 47 (FIG. 3) must be lifted off the opening 51, because the valves 16 are closed as long as the membrane 47 closes the opening 51 and thus maintains the overpressure in the supply line 17. For this purpose, the line 65, 65" etc. of each rapid depressurizer 11, 11 etc. is connected to the preferred output Y, of a correlated monostable element M, M" etc., whose signal generates an overpressure on the side of the membrane 47 facing away from the opening 51. The control input X, of each monostable element M, M" etc. is connected to the output Y of a preceding And element U, U" etc., of which an input X, is connected to the output Y, of a preceding bistable element B, B" etc. The other input X,, of the And elements u, U correlated with the odd rapid depressurizers 11, 11 are connected, via a first amplifier 77, to the first output A, of the pulse transmitter 76, while the other output X, of the And elements U, U" correlated with the even rapid depressurizers 11", 11" are connected, via a second amplifier 78, to the second output A, of the pulse transmitter 76. The control inputs X, of the bistable elements B, B etc. are connected to the instable output Y, of the monostable element M, M etc. whichprecedes in the control cycle. The other control input X, of the bistable element B, B is connected to the output Y, of the bistable element B, B" etc. which follow next in the flushing cycle. The control input X, of the bistable element B, which is first in the flushing cycle, is connected to the instable output Y, of the monostable element M", which is last in the flushingcycle. In outputY, is connected to the control input X, of the bistable element B which comes last in the flushing cycle.

The circuit described operates as follows: When the difference P3 P1 of the pressures in the dust air chamber 1 and in the clean air chamber 9 exceeds a certain value, the pressure differential switch 66 produces a signal to the control input X, of the bistable element B which, in turn, gives a signal from the control output Y, to the amplifier 70 which feeds all monostable elements M to M through the reducing valve 71. This causes the membranes 47 in each of the rapid depressurizers 11' to l1 (see FIGS. 2 and 3) to be pressed against the opening 51. At the same time, the amplifier 70 gives a signal to the: valve 72 connecting the flushing air chamber 7 with the compressed air source 19 on the one hand, and generating through the throttle valve 74 an overpressure in the lines 17 and 21 (see FIGS. 2 and 4) on the other, thus closing the valves 16. After a certain period of time, adjustable by means of the throttle valve 73, the pressure P2 in the flushing air chamber 7 attains a certain value. When this value is reached, the pressure switch 75 is actuated which emits a signal to the control input X of the Or- Nor key element 0. This causes the Or-Nor key element to reverse, controlling through its output Y, the inputs E, and E of the pulse transmitter 76. Upon the first signal of the Or-Nor key element O-after the start ofa dust collecting campaign-the pulse transmitter 76 gives a pulse through the first output A, to the inputs X, of the And elements U, U" etc. correlated with the odd rapid depressurizers ll, 11 etc. The first bistable element B of the bistable elements B, B" etc. which precede these odd And elements U, U" etc. gives a signal from the output Y, to the input X, of the And element U, whereas the other odd bistable element B'" etc. continues to blow a signal through their output Y,. Thus, the first odd And element U generates a signal from its output Y to the input X of the monostable element M. The monostable element M reverses and gives a signal through its not preferred output Y, to the input X, of the succeeding even bista ble element B". At the same time, a venting of the rapid depressurizer 11' takes place which means that the pressure built up behind the membrane 47 by the monostable element M drops. This causes the pressure in the lines 17, 21 (see FIGS. 2 and 4) to collapse and a flushing air blast ensues.

Due to the reversal of the bistable element B succeeding the monostable element M, the former generates a signal to the control input X, of the bistable element B which precedes in the flushing cycle. In addition, the bistable element B" gives a signal from the output Y, to the input X, of the succeeding And element U". The signal to the control input X, of the first bistable element B interrupts the signal to the control input X of the monostable element M, whereupon the latter again emits a signal through the stable output Y, to the rapid depressurizer 11, thereby causing the termination of the flushing air blast.

In consequence of the flushing air blast, there is a drop in the pressure P2 in the flushing air chamber 7, causing the pressure switch 75 to switch the Or-Nor key element 0 to the preferred output Y, and interrupting the signal to the pulse transmitter 76. depressurizers As soon as the pressure P2 in the flushing air chamber 7 has again reached the certain value mentioned, there is a second signal from the pressure switch 75 to the Or-Nor key element 0 and a signal from the latter to the pulse transmitter 76 which sends a pulse from its second output A, to all And elements U", U etc. correlated with the even rapid depresurizers ll, 11" etc. The second And element U, which is already receiving a signal at its input X, from the bistable element B", now receives a pulse at its input X, and controls from output Y the input X of the monostable element M" which reverses to its not preferred output Y,. This causes the rapid depressurizer 11 to be depressurized, and a blast of flushing air into the filter hoses 2 correlated with it ensues until the succeeding bistable element 8 sends from its output Y, signal to the control input X, of the bistable element B", thereby interrupting the signal to the control input X of the monostable element M" and terminating the flushing air blast. The pressure drop occurring in the flushing air chamber 7 during this flushing air blast shuts off the pulse transmitter 76 through the pressure switch 76 and the Or-Nor key element 0.

As soon as the pressure P2 in the flushing air chamber 7 has regained the certain value mentioned, there is, through the pressure switch and the Or-Nor key element 0, a pulse by the pulse transmitter 76 from the first output A, to the inputs X, of the And elements U, U'" etc. correlated with the odd rapid depressurizers 11, 11" etc. Since only the And element U of the odd And elements U, U'" etc. receives a signal at its input X,, it generates a signal to the control input X of the succeeding monostable element M'", whereupon the rapid depressurizer 11" is depressurized, a flushing air blast ensuing in the filter hoses 2 associated with it. The flushing air blast is terminated in the manner described above with reference to the rapid depressurizers 11, and 11'. The flushing cycle continues in the described manner to the pressurization of the last rapid depressurizer 11". During the pressurization of the last rapid depressurizer 11", there is a signal through the output Y, of the monostable element M which is conducted to the control input X, of the bistable element B and the control input X, of the bistable element B. The bistable element B then generates a signal from its output Y, to the input X, of the succeeding And element U, thereby readying the circuit for a new flushing cycle. The same signal proceeds from the output Y, of the bistable element B to the control input X, of the last bistable element B, and the rapid depressurizer 11" is pressurized anew. The signal to the control input X, of the bistable element B remains without influence as long as the latter receives a signal to its control input X, from the pressure differential switch 66.

To stop the dust collection system, the dust air supply is turned off so that the pressure differential P3 P1 between the dust air chamber and the clean air chamber becomes zero. This eliminates the signal to the input X, of the bistable element B so that it reverses upon the arrival of a signal from the monostable element M at the end of a flushing cycle, terminating the signal emanating from the output Y This interrupts the supply of air through the amplifier 70, and the feed current to the monostable element M etc. is thus shut off.

The outputs A, and A, of the pulse transmitter 76 are connected respectively to the output Y of a correlated And element U, and U The inputs X, of the two And elements U, and U, are connected respectively, via a time delay member C, and C to the output Y, ofa correlated bistable element B, and 8,. The outputs Y of the And elements U, and U,,, in addition, are each connected to the control inputs X, of the respective bistable elements B, and B, correlated with the other output. The output Y, of the bistable elements B, and B is connected respectively to the control input X, of the bistable element correlated with the other output. The input X, of the And elements is connected to the not preferred output Y, of the Or-Nor key element 0.

If a signal emanates from the not preferred output Y, of the Or-Nor key element to the inputs X of the And elements U, and U then the first Andelement U,-in the absence of a signal from the input X,, a signal to the input X of the second And element U then being impossible-sends a signal to the output A and to the control input X; of the second bistable element 8;. The signal thus generated at the output Y of the second bistable element B reaches the input X, of the second And element U with the time delay due to the time delay member C The time delay in the time delay member C, must be. so chosen thatthe signal from the Or-Nor key element 0 due to the pressure drop in the flushing air chamber during the flushing air blast is interrupted within this time delay. When a new signal emanates from the Or-Nor key element 0 due to the pressure in the flushing air chamber 7 having risen again, the second And element U will respond, giving a signal to the second output A of the pulse transmitter 76 and to the control input X of the first bistable element 8, which sends a signal to the input X, of the first And element U, with time delay due to the time delay member C whereupon the first And element U, is ready for a new signal through the output A and the described process repeats itself.

FIG. 6 shows a vertical section of the pressureswitch 76 in enlarged view. Disposed in the wall of the flushing air chamber 7 is an opening which is closed by aflexible membrane 79. Fastened to said membrane is a central pin 80 projecting outward. A line82 extendsaxial to the pin 80, and through a wall ofa housing 81 which is attached to the outsideof theflushing air chamber 7. Between the end .of the line 82 and the pin 80 is mounted a lever 83 which can pivot about a fixed shaft 84, the lever being provided with a packing 85. There is further screwed into the wall of the housing 81 an adjusting screw 86 by means of which the initial tension of a helical spring 87 is adjustable, the spring being disposed axial to the adjusting screw 86 between the latter and the free end of the lever 83. The lever 83 is pushed against the pin 80by the action of the spring 87. The .line 82 connects to the control input X of the Or- Nor key element 0. If the pressure P2 in the flushing air chamber 7 exceeds a certain value, the membrane 79 is bulged outward so that the pin 80 presses the packing- 85 against the mouth of the line 82, closing it. As soon as the mouth of the line 82 is closed by the packing 85, the Or-Nor key element 0 reverses and emits a signal from its instable output Y The time interval between two flushing blasts can be I varied by adjusting the throttle valve 73 (FIG. The duration ofa flushing blast can be freely selected by adjusting the throttle valve 74.

According to an implementation example (not illustrated) the pressure differential switch 66, the bistable element B, the amplifier 70 and the valve 72 are eliminated (see FIG. 5). The throttle valves 73 and 74 as well as the reducing valve 71 are then connected directly to the compressed air source 19. The input X of the first bistable element B is preceded by a manually operated starting elementcapable of producing a signal to the input X It is self-suggesting to the specialist to operate the dust collecting system with a suitable gas other than the above-described flushing air.

instead of the elements of the fluid mechanism described, other controlssuch as pneumatic logic elements with moving parts or electronic logic elements may be employed for the control of the rapid depressurization.

According to another implementation example not illustrated, the rapid depressurizers may be eliminated. One or more of the annular membranes are then pressurized or depressurized directly by a fluid mechanism with a great exhaust air current.

FIG. 7 shows another embodiment which includes a pneumatic valve 16 with a double filter hose 2'. The double filter hose 2' has an external filter hose 2" and an internal filter hose 2", coaxial to and spaced from the fonner. The ends of the filter hoses 2" and 2" facing away from the valve 16' are firmly interconnected and they close off the interior of the filter hose 2' against the dust air chamber 1. The end of the internal filter hose 2" facing the valve 16' is closed. In this embodiment, the flushing air blast is aimed and unbraked between the filter hoses 2" and 2" because the internal filter hose 2" is disposed so as to be coaxial with and spaced from the connecting tube 15' and has approximately the same outside diameter as the tube. In contrast to the known flushing air valves, the flushing air does not impinge the closing surface 89 of the internal filter hose 2", thus avoiding a backwash of the flushing air blast. in addition, this combination offers the advantage of reducing the mechanical stress on the filter hoses.

What is claimed is:

1. A pneumatic dust collection system, comprising a housing defining a dust air chamber portion, a flushing air chamber portion and a clean-air portion arranged one after the other and with a first separating wall between said clean-air portion and said flushing air portion and a second separating wall between said flushing-air portion and said dust air portion, at least one filter hose disposed in said dust air chamber portion, a connecting tube extending axially through said second separating wall into one end of said filter hose and connecting the interior of said filter hose to said clean-air chamber portion and being spaced from the interior of said filter hose to define an annular flow passage between said connecting tube and said filter hose and from said dust air chamber to said flushing air chamber, an inflatable annular member located in 'said flow passage and being inflatable to close said flow passage, and control air passage means connected to said flushing chamber and said flow chamber for deflating and inflating said membrane and for filling the flushing chamber with flushing air before said membrane is deflated to open said air flow passage.

2. A pneumatic dust collection system, according to claim 1, wherein there are a plurality of filter hoses in said dust air chamber, each having an annular membrane for opening and closing said flow passage, said control air passage means including a control line c0nnected to said inflatable membranes for pressurizing and depressurizing said membranes, compressed air supply means connected to said control line, and a rapid depressurizer member connected to said control line.

3. A pneumatic dust collection system, according to claim 1, wherein said collecting tube includes an annular bead extending into said flow passage and forming a valve seat for said inflatable membrane.

4. A pneumatic dust collection system, according to claim 1, including a sleeve member connected to said second partition wall and having a portion extending into said dust air chamber, said filter hose being engaged around said sleeve member, said inflatable membrane being located between said sleeve member and said second separating wall between said flushing chamber and said dust air chamber.

5. A pneumatic dust collector, according to claim 4, wherein said sleeve member includes a flange, an annular member disposed between said flange and said second separating wall, said inflatable member bring engaged over said annular member, said annular member having a passage therein for the flow of inflation air to inflate said inflatable membrane, and fastening means extending through said flange and said annular member to fasten said flange and said annular member to said second separating wall.

6. A pneumatic dust collection system, according to claim 5, wherein said annular member has an interior concave surface covered by said inflatable membrane.

7. A pneumatic dust system, according to claim 1, wherein said control air passage means includes an air pressure control line extending into said flushing chamber and having connections to said inflatable membrane, a rapid depressurizer control connected to said control line, said depressurizer including a valve member having a wall with an opening which communicates with said control line, an annular wall at the interior of said member arranged around said opening, a flexible diaphragm covering said annular wall and forming a pressure chamber in said body connected to said control line, said membrane extending radially beyond said pressure chamber, and 'a cover supporting the annular periphery of said membrane closing the opposite side of said body and forming a pressure equalizing chamber on the opposite side of said diaphragm, said diaphragm having a hole extending therethrough communicating with said pressure chamber, an intermediate housing mounted on said cover having an opening in one end communicating with said pressure equalizing chamber of said cover, said intermediate housing defining an annular lip around said opening forming a seat, a diaphragm stretched across said seat enclosing said seat and having an opening therethrough, the space around said forming a venting chamber to the atmosphere, the opening of said intermediate housing being communicatable when said membrane is lifted from said annular seat to said venting chamber, and closing means covering said intermediate housing having a cavity which is pressurizable or depressurizable by a fluid mechanism element.

8. A pneumatic dust system, according to claim 7, including a second intermediate housing with a venting chamber (52) said diaphragm (46) extending beyond said opening (49) radially and joined peripherally to said second intermediate housing (43) for the formation of said cavity, said second venting chamber (52) being connected through an opening (50) in said second membrane (46) and through an opening (51) in said wall of said second housing (43), the opening (51) being closable by means of a third membrane (47) enclosing with a cover (44) a cavity which is pressurizable and depressurizable by means of the fluid mechanism element.

9. A pneumatic dust collection system, according to claim 7, wherein said annular membrane is pressurizable by a compressed air source and depressurizable by means of said control members, said control members providing fluid mechanism elements.

10. A pneumatic dust collection system, according to claim 2, wherein said rapid depressurizer is connected to signal means including a preferred output (Y1) of a monostable fluid mechanism element (M), said signal being responsive to an overpressure in said flushing air chamber to control input (X) of said monostable element (M).

11. Pneumatic dust collection system, according to subclaim 10, characterized in that a pressure differential switch (66) is provided in order to open the supply current line between the monostable element (M) and the compressed air source (19) above a certain pressure differential (P3 Pl) between the dust air chamber (1) and the clean air chamber (9), and to close it below said certain pressure differential.

12. Pneumatic dust collection system, according to sub-claim 10, characterized in that several rapid depressurizers (11' to 11'') with correlated valves (16) are present; in that the control input (X) of the monostable element (M to M") of each rapid depressurizer is connected to the output (Y) of a correlated And element (U' to U"); in that the one input (X of the And element U to U") is connected to the output of a preceding, bistable element (3' to B"); in that the control input (X of each bistable element (8' to B") is connected to the output (Y of the bistable element succeeding the correlated monostable element, the control input (X,) of said bistable element being connected to the not preferred output (Y of the preceding monostable element; in that the second inputs (X of the odd And elements (U', U etc.) are connected to the first output (A, ofa pulse transmitter (76); and in that the second inputs (X of the even And elements (U, U" etc.) are connected to the second output (A of the pulse transmitter (76) which, upon he repeated attainment of the preselected flushing pressure (P2) in the flushing air chamber (7), generates an alternating pulse through the outputs (A and A 13. Pneumatic dust collection system, according to subclaim 12, characterized in that, for the purpose of triggering a flushing cycle, the signal output of the pressure differential switch (66) is connected to the control input (X of a bistable element (B) which opens, by signal through its output (Y,), a pneumatic amplifier (70) in the supply current line of the monostable elements (M' to M") and in that, for the purpose of terminating a flushing cycle, the control input (X2) of the bistable element (B) is connected to the instable' output (Y,) of the last monostable element (M').

14. Pneumatic dust collection system, according to subclaim 12, characterized in that the pulse transmitter (76) has two inputs (E E each of which being connected to the input (X,) of a correlated end element (U,, U,) whose outputs (Y) are respectively connected to the outputs (A,, A,); in that the input (X,) of each And element (U,, U,) is connected, via a time delay member each (C C to the output (Y,) of a correlated bistable element (8,, 8,); in that the output (Y) of each And element (U U is connected to the input (X,) of the bistable element correlated with the other And element; and in that each output (Y of the bistable elements (8,, 8,) is connected to the input (X,) of the other bistable element.

15. Pneumatic dust collection system, according to subclaim 14, characterized in that the two inputs (E,, E of the pulse transmitter (76) are connected to the output (Y of an Or-Nor key element whose input (X) is closable by a pressure switch (75) controllable by the pressure (p2) in the flushing air tank, in such a manner that the input (X) is closed when the pressure (p2) exceeds a certain value.

16. A pneumatic dust collection system, according to claim 1, wherein said filter hose comprises a double filter hose including an internal hose portion disposed coaxial to and spaced from the interior of said filter hose outer portion and having a closed inner end spaced from the inner end of said connecting tube having substantially the same diameter as said connecting tube.

17. A depressurizing valve for a control air pressure line of a valve for regulating the flow of a flushing air to the interior of a filter hose in a pneumatic dust collection system, comprising a valve body having a wall adapted to be connected to or formed as a wall of the flushing chamber and having a hollow interior with a first opening in said wall for communication to the flushing chamber, and a first annular wall surrounding the opening and forming a first seat, a first diaphragm extending across the interior of said valve body and over said first seat to close off a pressure chamber within said first annular wall and communication with said first opening, a cover extending over said first diaphragm and having a central second opening, a first intermediate tubular housing engaged over said cover and sealed peripherally around said second opening and having a central third opening communicating with said second opening, a second interior projection around said third opening defining a second seat, a second diaphragm extending across the interior of said first intermediate tubular housing and closing said second seat, a second intermediate housing engaged over said first intermediate housing and having a fourth opening in communication with the space between said second diaphragm and said second intermediate housing, a third diaphragm carried in said second intermediate housing said second intermediate housing having an opening with a third seat closed by said third diaphragm and a cover closing said second intermediate housingand having an opening for communication with a pressure air supply.

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1. A pneumatic dust collection system, comprising a housing defining a dust air chamber portion, a flushing air chamber portion and a clean-air portion arranged one after the other and with a first separating wall between said clean-air portion and said flushing air portion and a second separating wall between said flushing-air portion and said dust air portion, at least one filter hose disposed in said dust air chamber portion, a connecting tube extending axially through said second separating wall into one end of said filter hose and connecting the interior of said filter hose to said clean-air chamber portion and being spaced from the interior of said filter hose to define an annular flow passage between said connecting tube and said filter hose and from said dust air chamber to said flushing air chamber, an inflatable annular member located in said flow passage and being inflatable to close said flow passage, and control air passage means connected to said flushing chamber and said flow chamber for deflating and inflating said membrane and for filling the flushing chamber with flushing air before said membrane is deflated to open said air flow passage.
 2. A pneumatic dust collection system, according to claim 1, wherein there are a plurality of filter hoses in said dust air chamber, each having an annular membrane for opening and closing said flow passage, said control air passage means including a control line connected to said inflatable membranes for pressurizing and depressurizing said membranes, compressed air supply means connected to said control line, and a rapid depressurizer member connected to said control line.
 3. A pneumatic dust collection system, according to claim 1, wherein said collecting tube includes an annular bead extending into said flow passage and forming a valve seat for said inflatable membrane.
 4. A pneumatic dust collection system, according to claim 1, including a sleeve member connected to said second partition wall and having a portion extending into said dust air chamber, said filter hose being engaged around said sleeve member, said inflatable membrane being located between said sleeve member and said second separating wall between said flushing chamber and said dust air chamber.
 5. A pneumatic dust collector, according to claim 4, wherein said sleeve member includes a flange, an annular member disposed between said flange and said second separating wall, said inflatable member bring engaged over said annular member, said annular member having a passage therein for the flow of inflation air to inflate said inflatable membrane, and fastening means extending through said flange and said annular member to fasten said flange and said annular member to said second separating wall.
 6. A pneumatic dust collection system, according to claim 5, wherein said annular member has an interior concave surface covered by said inflatable membrane.
 7. A pneumatic dust system, according to claim 1, wherein said control air passage means includes an air pressure control line extending into said flushing chamber and having connections to said inflatable membrane, a rapid depressurizer control connected to said control line, said depressurizer including a valve member having a wall with an opening which communicates with said control line, an annular wall at the interior of said member arranged around said opening, a flexible diaphragm covering said annular wall and forming a pressure chamber in said body connected to said control line, said membrane extending radially beyond said pressure chamber, and a cover supporting the annular periphery of said membrane closing the opposite side of said body and forming a pressure equalizing chamber on the opposite side of said diaphragm, said diaphragm having a hole extending therethrough communicating with said pressure chamber, an intErmediate housing mounted on said cover having an opening in one end communicating with said pressure equalizing chamber of said cover, said intermediate housing defining an annular lip around said opening forming a seat, a diaphragm stretched across said seat enclosing said seat and having an opening therethrough, the space around said forming a venting chamber to the atmosphere, the opening of said intermediate housing being communicatable when said membrane is lifted from said annular seat to said venting chamber, and closing means covering said intermediate housing having a cavity which is pressurizable or depressurizable by a fluid mechanism element.
 8. A pneumatic dust system, according to claim 7, including a second intermediate housing with a venting chamber (52) said diaphragm (46) extending beyond said opening (49) radially and joined peripherally to said second intermediate housing (43) for the formation of said cavity, said second venting chamber (52) being connected through an opening (50) in said second membrane (46) and through an opening (51) in said wall of said second housing (43), the opening (51) being closable by means of a third membrane (47) enclosing with a cover (44) a cavity which is pressurizable and depressurizable by means of the fluid mechanism element.
 9. A pneumatic dust collection system, according to claim 7, wherein said annular membrane is pressurizable by a compressed air source and depressurizable by means of said control members, said control members providing fluid mechanism elements.
 10. A pneumatic dust collection system, according to claim 2, wherein said rapid depressurizer is connected to signal means including a preferred output (Y1) of a monostable fluid mechanism element (M), said signal being responsive to an overpressure in said flushing air chamber to control input (X) of said monostable element (M).
 11. Pneumatic dust collection system, according to subclaim 10, characterized in that a pressure differential switch (66) is provided in order to open the supply current line between the monostable element (M) and the compressed air source (19) above a certain pressure differential (P3 - P1) between the dust air chamber (1) and the clean air chamber (9), and to close it below said certain pressure differential.
 12. Pneumatic dust collection system, according to sub-claim 10, characterized in that several rapid depressurizers (11'' to 11n) with correlated valves (16) are present; in that the control input (X) of the monostable element (M'' to Mn) of each rapid depressurizer is connected to the output (Y) of a correlated And element (U'' to Un); in that the one input (X1) of the And element U'' to Un) is connected to the output of a preceding, bistable element (B'' to Bn); in that the control input (X2) of each bistable element (B'' to Bn) is connected to the output (Y2) of the bistable element succeeding the correlated monostable element, the control input (X1) of said bistable element being connected to the not preferred output (Y2) of the preceding monostable element; in that the second inputs (X2) of the odd And elements (U'', U'''''' etc.) are connected to the first output (A1) of a pulse transmitter (76); and in that the second inputs (X2) of the even And elements (U'''', U'''''''' etc.) are connected to the second output (A2) of the pulse transmitter (76) which, upon the repeated attainment of the preselected flushing pressure (P2) in the flushing air chamber (7), generates an alternating pulse through the outputs (A1 and A2).
 13. Pneumatic dust collection system, according to subclaim 12, characterized in that, for the purpose of triggering a flushing cycle, the signal output of the pressure differential switch (66) is connected to the control input (X1) of a bistable element (B) which opens, by signal through its output (Y2), a pneumatic amplifier (70) in the supply current line of the monostable elements (M'' to M'''') and in that, for the purpose of terminating a flushing cycle, the control input (X2) of the bistable element (B) is connected to the instable output (Y2) of the last monostable element (Mn).
 14. Pneumatic dust collection system, according to subclaim 12, characterized in that the pulse transmitter (76) has two inputs (E1, E2), each of which being connected to the input (X2) of a correlated end element (U1, U2) whose outputs (Y) are respectively connected to the outputs (A1, A2); in that the input (X1) of each And element (U1, U2) is connected, via a time delay member each (C1, C2), to the output (Y1) of a correlated bistable element (B1, B2); in that the output (Y) of each And element (U1, U2) is connected to the input (X2) of the bistable element correlated with the other And element; and in that each output (Y1) of the bistable elements (B1, B2) is connected to the input (X1) of the other bistable element.
 15. Pneumatic dust collection system, according to subclaim 14, characterized in that the two inputs (E1, E2) of the pulse transmitter (76) are connected to the output (Y1) of an Or-Nor key element (O) whose input (X) is closable by a pressure switch (75) controllable by the pressure (p2) in the flushing air tank, in such a manner that the input (X) is closed when the pressure (p2) exceeds a certain value.
 16. A pneumatic dust collection system, according to claim 1, wherein said filter hose comprises a double filter hose including an internal hose portion disposed coaxial to and spaced from the interior of said filter hose outer portion and having a closed inner end spaced from the inner end of said connecting tube having substantially the same diameter as said connecting tube.
 17. A depressurizing valve for a control air pressure line of a valve for regulating the flow of a flushing air to the interior of a filter hose in a pneumatic dust collection system, comprising a valve body having a wall adapted to be connected to or formed as a wall of the flushing chamber and having a hollow interior with a first opening in said wall for communication to the flushing chamber, and a first annular wall surrounding the opening and forming a first seat, a first diaphragm extending across the interior of said valve body and over said first seat to close off a pressure chamber within said first annular wall and communication with said first opening, a cover extending over said first diaphragm and having a central second opening, a first intermediate tubular housing engaged over said cover and sealed peripherally around said second opening and having a central third opening communicating with said second opening, a second interior projection around said third opening defining a second seat, a second diaphragm extending across the interior of said first intermediate tubular housing and closing said second seat, a second intermediate housing engaged over said first intermediate housing and having a fourth opening in communication with the space between said second diaphragm and said second intermediate housing, a third diaphragm carried in said second intermediate housing said second intermediate housing having an opening with a third seat closed by said third diaphragm and a cover closing said second intermediate housing and having an opening for communication with a pressure air supply. 